Edit in JSFiddle

<p>
    <label class="switch">
        <input type="checkbox" />
        <span class="label">
            <span class="on">ON</span
            ><span class="separator"></span
            ><span class="off">OFF</span>
        </span>
    </label>
</p>
<p>
    <label class="switch">
        <input type="checkbox" checked />
        <span class="label">
            <span class="on">ON</span
            ><span class="separator"></span
            ><span class="off">OFF</span>
        </span>
    </label>
</p>

.switch {
    border: solid 1px #ccc;
    border-radius: 20px;
    display: inline-block;
    height: 40px;
    overflow: hidden;
    -ms-user-select: none;
    -moz-user-select: none;
    -o-user-select: none;
    -webkit-user-select: none;
    user-select: none;
    width: 100px;
}
.switch [type=checkbox] {
    display: none;
}
.switch .label {
    cursor: pointer;
    margin-left: -60px;
    -ms-transition: margin .1s;
    -moz-transition: margin .1s;
    -o-transition: margin .1s;
    -webkit-transition: margin .1s;
    transition: margin .1s;
    white-space: nowrap;
}
.switch :checked + .label {
    margin-left: 0;
}
.switch .label > * {
    vertical-align: top;
}
.switch .on,
.switch .off {
    display: inline-block;
    height: 40px;
    line-height: 40px;
    text-align: center;
    width: 80px;
}
.switch .on {
    background-color: #00f;
    background-image: -ms-linear-gradient(
        top,
        hsl(214,90%,40%),
        hsl(214,90%,70%)
        );
    background-image: -moz-linear-gradient(
        top,
        hsl(214,90%,40%),
        hsl(214,90%,70%)
        );
    background-image: -o-linear-gradient(
        top,
        hsl(214,90%,40%),
        hsl(214,90%,70%)
        );
    background-image: -webkit-linear-gradient(
        top,
        hsl(214,90%,40%),
        hsl(214,90%,70%)
        );
    background-image: linear-gradient(
        top,
        hsl(214,90%,40%),
        hsl(214,90%,70%)
        );
    box-shadow:
        3px 2px 10px rgba(0,0,0,.2) inset,
        -3px 2px 10px rgba(0,0,0,.2) inset;
    color: #fff;
    text-shadow: -1px -1px rgba(0,0,0,.3);

}
.switch .separator {
    background-color: #eee;
    border: solid 1px #999;
    border-radius: 50%;
    box-sizing: border-box;
    box-shadow:
         1px 2px #fff inset,
        -1px 2px #fff inset,
        1px 1px 5px rgba(0,0,0,.2);
    display: inline-block;
    height: 40px;
    margin: 0 -20px;
    position: relative;
    width: 40px;
}
.switch .off {
    background-color: #eee;
    box-shadow: 5px 5px 10px rgba(0,0,0,.2) inset;
    color: #777;
    text-shadow: 1px 1px #fff;
}